I assume it has to be a power tool. In other words, I can't hand in an old screwdriver as the 'tool' eligible for trade in.

Tyler from Festool USA has confirmed it can be pretty much anything, an allen wench, a busted tape measure... does NOT have to be an actual power tool, nor an equivalent item to whatever Festool you decide to purchase.

Curious as to why the ts75 was excluded when all the other saws are part of the deal. I was excited...then I was not.

Just a guess but they probably don't run as big of an inventory of them as they probably sell at a fraction of the rate of the ts55. Folks probably by a high ratio buy a ts55 first and then later buy a ts75 instead of starting with the ts75

A saw like the hk55 is probably something they really don't sell many of but expected to sell more of, so probably why it is there.

No matter the official reason ever given for such things "get folks off fence", which I won't doubt is at some level an honest reason on Festools part. You usually do a selective sale like this to either bring down inventory of stuff that hasn't moved as you hoped, clear some space for new stuff that might slow sales of current inventory, or pull people in with the core introductory tools.

I'm hoping they are preparing to start selling both the metric and imperial tools, so they are trying to sell down the imperial inventory some before re-introducing the metric ones. There now being a simple way to buy the metric scale for the routers gives me a bit more hope of this. I don't think they want to have a bunch of retailers with a stock room of imperial tools, if they start offering the metric ones again too. Sure there will be folks who want the imperial tools, but they certainly won't sell at the rate they did before. Wouldn't make your retailers very happy if they find themselves with stuff not moving the same.